I am working on e2e, benchmarking tests for the official Prometheus project which would take at least 24h so we don’t want to run these for all PRs

The idea is that when the PR might affect the performance or the PR is for a new release, one of the maintainers will simply add a label that will trigger a specific job.
The git tags can be used as a workaround, but that would mean asking the PR author to add a tag.
Using labels will skip this step so when a maintainers considers a PR for performance testing can just add the label and start the tests.

While the interaction is slightly different, I think they probably end up working in very similar ways under the hood. I would recommend (if you don’t mind) creating a github issue that proposes how this would work in greater detail. For example would adding or removing labels trigger a new build? Or would we only take labels into account when on subsequent pushes?